Myth of Jesus, page-322

"God in Three Persons: A Doctrine We Barely Understand"
It is barely understood only because of the attempt to shoehorn Jesus into the role of God.
Nothing more nothing less.

It possibly started from attempts by John and Paul to elevate Jesus to the ranks of Divinity which was common in the Roman and Greek worlds, mixed in with symbols used to describe creation as derived via 3 primary "impulses/forces".
Eg Male + Female + Joining = New birth.

Whilst the two obvious ones are well recognized, usually the more subtle 3rd factor .. in this case "joining together", is not, though it is equally necessary.

"The word trinity comes from "tri" meaning three and "unity" meaning one."
This is a made up meaning of "trinity" to suit the authors beliefs.

Oxford Dictionary:
Trinity (Latin: Trinitas, lit. 'triad', from trinus, "threefold")

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